Breast cancer remains the most common cancer for women and perhaps their most feared medical diagnosis. Although much is known about the etiology of breast cancer, questions remain about environmental factors that initiate breast cancer carcinogenesis and when they act during the lifespan. The Bay Area Breast Cancer and the Environment Research Center (BABCERC), based at the University of California San Francisco Compre- hensive Cancer Center under the leadership of Dr. Robert A. Hiatt, Director of Population Sciences, will addres., the on-going concerns about the environmental etiology of breast cancer by focusing on mammary gland develop- ment during puberty when the breast may be especially vulnerable to environmental influences. At the same time it will create a unique organizational infrastructure for enhancing the existing partnership of scientists with local community and advocacy groups following the principles of community-based participatory research. The Bay Area is well suited for such a Center because rates of breast cancer there have been reported as the highest in the nation and there is high interest and cooperation from involved community members, government leaders, health departments, academic institutions and advocacy groups. Project 1 will study mammary cells and the mammary microenvironment in normal and cancer prone mice during all stages of development to determine the effects of exposure to prototypical environmental stressors in this model and develop in vitro mechanism-based screens to detect agents with possible mammary gland carcinogenicity. Project 2 proposes to recruit a cohort of approximately 400 7-8 year old girls from the Kaiser Foundation Health Plan and follow them through the pubertal transition. Data will be collected during a 6 year follow-up period from questionnaires, physical examination, and biospecimens that will allow analyses of links between environmental factors and mammary development, including the possible importance of susceptibility associated with selected gene-environment interactions. The Community Outreach and Translational Core will be directed and comprised of leaders in the local breast cancer advocacy movements in Marin and San Francisco Counties, who are highly experienced working with their respective communities on the topic of this research. The COTC activities are both highly integrated and interactive with the research projects and well connected to the community and its concerns. By incorporating the skills of a broad spectrum of expertise in fields such as developmental biology, epidemiology, and community advocacy, the BABCERC will provide an exciting opportunity for transdisciplinary research on a significant societal and biomedical challenge...understanding the relationship of breast cancer to the environment.